Currently, there exist two main therapies to relieve edema: medicinal diuretics and hemodialysis. A method utilizing medicinal diuretics uses medicine to increase the volume of patients' urine, thereby drawing out the excess water in the body. Hemodialysis involves withdrawing patients' blood, and filtering the blood with an in vitro instrument to remove excess water. Then, the concentrated blood is transferred back into the body to relieve the edema.
Hemodialysis is also a regular treatment of acute or chronic renal dysfunction, acute drug poisoning, and pesticide poisoning. Tens of millions of patients with chronic renal failure use hemodialysis as regular treatment to sustain life, and the population of patients increases year by year. Dialysis involves a dialysate solution on both sides of a semipermeable membrane flowing from a first, high concentration side to a second, low concentration side by way of diffusion, osmosis and ultrafiltration until reaching dynamic equilibrium. By dispersion and ultrafiltration between blood and a dialysate solution, hemodialysis is achieved.
Each therapy currently has significant disadvantages. Medicinal diuretics may require a large number of medicines, which may cause side effects and drug resistance. Moreover, critically ill patients may suffer with kidney failure, thus blocking the diuresis. Furthermore, hemodialysis typically requires withdrawing blood from the body, which may change a patient's blood volume sharply and cause instabilities in blood pressure and even death. Hemodialysis can only last for several hours, so it cannot provide sustained, long-term and steady dialysis for patients. In addition, the dialysis equipment is too large to transfer easily, thus the patient will always need to be transferred to a dialysis room or the dialysis machine will need to be transferred to the patients' bedside—increasing the difficulty of the treatment. Moreover, the equipment is expensive and may cost millions of dollars. Unfortunately, these deficiencies have never been addressed previously.